Thermo relay



Jan. 26, 1932. A Q ET AL 1,842,958

THERMO RELAY Filed Nov. 29, 1927 Inventors Charles H.Chapman George R.Townsend Their Attorneg Patented Jan. 26, 1932 .Uiwrso STATES PATENT OFFICE CHARLES H. CHAPMAN, OF SGOTIA, AND GEORGE R. TOWNSEND, F SCHENECTADY, NEW YORK, ASSIGNOBS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK THERMO RELAY tion is to provide a more efiicient form of.

electrical heater unit for the thermo relay with improved construction whereby the heater unit practioally surrounds the thermo responsive elemen and also may be readily mounted and dismounted in a simple manner.

A still further object of the invention is to provide for varying the rating of the thermo relay simply by changing the heater element.

Another object of the invention is to provide a thermo relay switch construction permitting actuation of a common switch mem ber by'any one of a plurality of thermo responsive elements. I An additional object of the invention is to provide a thermo relay construction that may be readily mounted on the motor control panel with a minimum space requirement.

Other advantageous features of our invention will appear from the following description of the accompanying drawings, in which Fig. 1' is a front view of a motor control switch having our improved form of thermo overload relay associated therewith for affording overload protection to the motor; Fig. 2 is a side view ofthe switch shown in Fig. 1 with certain parts of the thermo relay broken away in order to more clearly reveal the details of the construction; Fig. 3 is a perspective view of the operating mechanism of the thermo relay; Fig. 4 is a perspective view of the heater base within which the electrical heating element for the thermo relay is mounted: Figs. 5 and 6 are perspective .views showing two of the forms of heating elements adapted for use with the heater base shown in Fig. 4, and Fig. 7 shows the heater base with the heater element cemented 1n place therein.

Referring to Fig. 1 it will be seen that our improved form of thermo relay is illus trated in connection with a motor starting switch of the improved form described and claimed in the copending application, Serial No. 241,950, Lewis J Weber, filed Dec. 22, 1927 and assigned to the assignee of our resent invention. It will be understood,

owever, that our improved thermo relay may be employed with advantage in other service. As shown in Fig. 1, the three-pole switch 10 is mounted upon the base 11 and 60 connected to be operated by the electromagnet 12 to control the circuit of a three-phase alternatin current motor or other similar electrical evice. Inasmuch as the details of construction of the switch mechanism itself 65 are not the essence of the present invention no further description thereof is deemed necessary.

Two thermo responsive actuating mechanisms 13 and 14 are provided for effecting the operation of the movable switch member 15. As illustrated the movable switch member 15 is shown connected to control the energizing circuit of the switch operating electromagnet 12 and the thermo responsive ac- 7 tuating mechanisms 13 and 14 each are connected in two of the phases of the threephase circuit controlled by the switch 10.

Each of the thermo responsive actuating units 13 and 14 comprises a thermo responsive element control actuating mechanism, such as shown in Fig. 3, and a heater unit for electrically heating the thermo responsive element such as shown in Fig. 7. As may be more clearly seen in Figs. 2 and 3 the actuating mechanism comprises a U-shaped frame 16 provided with a supporting arm 17 for carrying the adjusting lever 18, upon which the movable actuating element 19 is pivotally mounted. The actuating element 19 is .as of/the-well-known bimetallic type and is firmly secured at the end 22 to the frame 16 with the thermo\ element extending within 16 with the free end of the thermo element 21 in abutting engagement with the actuating member 19. The arrangement is suclr that when the thermo element 21 is suflicient- 1y heated the free end moves to the left out of engagement with the actuating member 19 to permit the biasing spring 20 to rotate the latter in a clockwise direction. The amount of movement ofthe free end 24 of the thermo element required to release the actuating element 19 is regulated by loosening the holding screw 25 and adjusting the lever 18.

In order to heat the thermo element 21 a heater unit of the form shown in Fig. 7 is arranged to be mounted in close proximity to the'thermo element. As shown in Figs. 1

. and 2 the heater unit consists of a casing 30,

33 having holes 34 formed therein.

. preferably formed of molded heat resisting material in channel-shape as indicated in Fig. 4. The bottom portion of the channelshaped casing is provided with a series of grooves 31 preferabl running diagonally across the panel as s own in Fig. 4. The casing 30 is adapted to receive an electrical heating element 32 such as shown in Figs. 5 and 6. This heater element, as shown in Fig. 5, is made of suitableheater material, such as nichrome or the like, in the form of a flat grid with relatively large flat terminals Thus heater element 32 may be placed within the channel casing 30 and imbedded in a cement 35 which is heat resisting, heat absorbing and heat conducting. As shown in. Fig. 7 the cement 35 flows into the grooves 31 formed in the casing and between the grids of the heater element and thereby provides a firm and secure anchorage of the heater element on the casing 30. The casing 30 is provided with openings 36 which register with the holes 34 in the terminals of the heater element. Inthis way the heater unit may be removably mounted on the conductor supports 37 and 38 by means of the two holding down screws 39 as is indicated in Figs. 1 and 2. It will be observed that the conductor supports 37 and 38 are mounted on the base 11 immediately adjacent the top and bottom of the thermo responsive actuating mechanism. Also these supports hold the heater unit in close proximity to the thermo responsive element 21 with the side legs of the casing 30 overlapping the side legs of' the channel shaped portion 23 of the frame 16. With this construction the conductor supports 37 and 38 and the heater casing 30 jointly serve to partially enclose the thermo responsive actuating mechanism which effectively protects the latter from mechanical injury. In addition the the channel-shaped portion 23 of the frame frame 16 enshroud the thermo responsive elev ment 21. This results not only in protecting the movable thermo responsive element from mechanical injury but also serves to confine the heat produced by the heating element in the region of the thermo responsive element while atthe same timepermitting ready mounting and unmounting of the heater unit. By thus substantially enclosing the thermo element 21 dissipation of heat by radiation and convection is greatly restricted, resulting in materially increasing the heat efiiciencv. Also the heat storage capacity provided by the heater casing 30, the cement 35 and to a lesser degree by the channel-sha ed portion 23 of the frame 16 enables the tlme required to heat the thermo responsive element to the operating temperature to be controlled. This is a desirable feature articularly where the thermo responsive evice is to afiord overload protection for the electric motors or the like as it enables the therheater element shown in Fig. 6 may readily than is provided by=the heater element 32 s with a lesser current. In other words, the wattage loss in each of the heater elements is substantially the same. By this arrangement the current carrying capacity of the thermo .relay mav be varied as desired by simply providing a series of heating elements ofdifier-ent current carrying capacity and each designed to produce the same watt loss. Thus to protect different size electric motors it is only necessary to change the heatingelements so as to correspond with the rating of the motors.

Where a plurality of the'thermo responsive actuating mechanisms are arranged actuate a common switch member, as shown in Figs. 1 and 2, the individual actuating members of each thermo element are arranged to act upon a common operating arm 40. As shown in Figs. ,1 and 2 the arm 40 and: into engagement with. t he cooperating.

.contact 41 as the arm 40 is raised and lowered, The actuatingmembers 19 of each of the thermo resnonl 'e devices are located below the arm 40 so as to engage therewith when released by movement of the free end of the thermo responsive elements 21. In order to 10 permitresetting of the actuating elements 9, a manual reset button 42 is arranged to ower the operating arm 40 against the bias of the springs 20 associated with the actuating elements :19.

devices to provide overload protection for a motor connected to be controlled by theswitch 10 is as follows: With the actuating elements 19 of the thermo responsive devices 6 held in abutting engagement with the free ends of the thermo responsive elements 21, the

' operating arm 40 maintains the movable contact 15 in engagement with the cooperating contact 41. This permits energization of the operating electromagnet for closing the switch 10. Upon closing of the switch 10 the heater elements 32 of each of the thermo relays ,will be heated in accordance with the. current flow in the corresponding phase of the motor cvircuit controlled by the switch. So long as conditions are normal, the heating effect produced by the heating elements is insufficient to cause actuation of the thermo responsive elements 21 to release either of 35 the spring bias actuating elements 19. However, in casethe current becomes excessive, for any reason, one or theother or both of the thermo elements are heated to the temperature required to effect release of the actuating element 19. For example in case the motor is stalled, both of the thermo elements would function if the adjusting lever 18 of the deviceis set to provide release under the same temperature conditions. In case one of the "phases of the circuit should fail, the remaining phase becomes overloaded andthe thermo device responsive to the heating effect of the current flow in the remaining phase then operates separately to operate the arms 40 to disengage the contact 15. In

any case as soon as the contact 15 is disengaged, the energizing circuit of the electromagnet 12 is interrupted, thereby permitting the switch 10 to open the overload circuit.

' To reset the thermo elements preparatory to subsequent operation of the switch 10 it is only necessary to wait a sufficient time for cooling and then to push the button 42, thereby lowering the arm 40 and resetting either or both of the actuating elements 19.

What we claim as new and desire to secure by Letters Patent of the United States, is,

1. A thermo responsive device comprising a movable thermo responsive element, and a removably mounted electrical heater unit The operation of the thermo responsive ing.

therefor having a heating element mounted in a casing of heat resisting material formede with an open recess in one side thereof shaped to receive and to partially surround the movable thermo responsive element. f

2. A thermo responsive device comprising a movable thermo responsive element fixed at one end, a support therefor having a channel shaped member disposed along one side of said thermo-responsive element, a coop- 15 crating channel-shaped member removably supported on the other side of said thermoresponsive element with the legs thereof in overlapping. relation with the legs of said first channel shaped member and thereby sub- 3 stantially surrounding said thermo element, and an electrical heater mounted within said removable channel member.

3, A thermo responsive device comprising a movable thermo responsive element, an'elec 35 trical -current conducting member for heating the thermo element, a channel-shaped casing of substantial heat storage capacity for housing the heater element and the thermo element therein, and a coatingof heat resisting on material for securing the heater element in the bottom of the channel-shaped casing and establishing a good heat conducting relationship between the heater element and the eas- V 4. A thermo responsive device comprising a movable thermo responsive element, an electrical heater element therefor having opening therein, and a channel-shaped casing of substantial heat storage capacity having grooves formed in the bottom thereof and provided with a heat resisting cement filling said openings and said grooves for holding the heater element in close heat conducting relation with the bottom of said casing.

5. A thermo responsive device comprising an actuating member, a movable thermo responsive element fixed at one end and having the other end free for controlling the acturating member, and an electrical heateru o mounted in opposing spaced relation with the thermo element and having a channel shaped easing substantially surrounding three sides of said thermo-responsive element and extending beyond the ends thereof with the heater enclosed between the casing and the movable thermo responsive element.

6. A thermo responsive device comprising a base, a U-shaped frame having one leg thereof mounted on said base, a movable thermo 12o responsive element secured at one end to the other leg of said frame and extending adja cent thereto, a spring bias actuating element mounted on the first leg of said frame to be controlled by the free end of said thermo element, a pair of current conducting supports each mounted on said base and extending adjacent opposite ends of said thermo element, and an electrical heater mounted in a casing of heat insulatingmaterial and arg x ranged to be electrically and mechanically connected with the ends of said current con-' ducting supports adjacent said movable thermo element. V V

7. A thermo responsive device comprising an actuating mechanism having a biased operating member and a movable thermo responsive controlling element therefor, a removable electrical heater unit having a channel shaped casing of heat insulating material attached thereto, and current conducting supports disposed adjacent the opposite ends of said movable thermo responsive element and arranged to be electrically and mechanically connected with said heater unit to supply heating current thereto and support the heater in heating relation with the movable thermo element with the casing of the heater partially surrounding the thermo element.

8. A thermo overload protective relay for multiphase alternating current circuits comprising a base, a movable switch member mounted on said base and having an actuating arm extending in spaced relation with the base on eitherside of said switch member, a thermo responsive actuating mechanism mounted on said base adjacent each end of said operating arm, each of said actuating mechanisms comprising a U-shape'd frame having one leg thereof mounted on said base with a spring bias actuating -mem-' ber pivotally mounted at the end thereof and extending into operating relation with said switch actuating arm, a movable thermo responsive element secured at one end on the other leg of said frame with the free end of the thermo element in abutting. engagement with-the end of said actuating member and a pair of current conducting supports mounted on the base adjacent opposite ends of said movable thermo element and adapted to be connected in a corresponding phase of the alternating current circuit, and an electrical ill) heating unit arranged to be electrically connected between said supports and mechanically supported thereby with the heater in heat conducting relation with said movable thermo responsive element.

9. A polyphase alternating current overload protective relay comprising a base, a'

switch member movably mounted on said base and having an actuating arm extending in spaced relation with the base on either side of said switch member, a pair of independently operable thermo responsive actuating mechanisms therefor mounted on said base adjacent the opposite ends of said actuating arm, each of said actuating mechanisms co1nprising a frame having a bimetal thermal element secured at one end thereto, and an actuating element pivotally mounted on the frame to be controlled by the free end of said thermal element, and biased to engage with said operating arm upon a predetermined movement of said free end of the thermal eleto be connected in a 

